Automotive interior trim panels are constructed in various forms including laminated structures wherein for example a stiff thin wall vinyl substrate supports a soft vinyl skin with a layer of urethane foam therebetween. The panel is then attached to the interior of an automobile on an assembly line by various forms of fasteners such as of the hook type and so-called "Christmas tree" type that are inserted and retained at their anchoring end in holes formed in the substrate. There may also be alignment pins that are similarly anchored to the substrate to aid in installation of the panel. The substrate can be molded in various ways such as by injection molding the article or vacuum forming a sheet of thermoplastic material such as expanded vinyl to the desired shape. As a cost saving measure, it is desirable that the fasteners be integrally joined with the substrate in the molding process rather than later attached thereto.
In injection molding, the molten plastic can be readily forced to surround an anchoring end of a fastener inserted in the mold cavity and then mechanically interlock therewith on solidification to firmly retain the fastener in place on the injection molded article. But this form of capturing and retaining a fastener by molding it in place with an equivalent mechanical interlocking relationship is not available with the vacuum forming process. In the latter process, the heated plastic sheet is normally drawn to the mold surface by withdrawing air through small vacuum holes provided therein. The vacuum holes are normally made small enough so as to not create dimples in the formed article and are spaced throughout the area of the mold surface to bring the heated plastic sheet into full area contact with the mold surface. But they are not suited to also drawing the heated sheet into full area contact with the interlocking surface of the anchor end of a fastener were it to be inserted in a cavity in this mold surface like in injection molding.